The invention is based on a device arrangement for exchanging data and on a process for operating such a device which generally includes a main station (master) and at least one secondary station (slave), which each have access via respective interfaces to at least one common data line. From European Patent Application EP-A 0 396 090, a generic device for exchanging data between a main station, called a master, and at least one secondary station, called a slave, is known. Both the master and the slaves have interfaces, which each access at least one common data line. The master can address all the slaves. A data transmission from a slave to the master that may possibly be necessary can be started by the slave itself without being ordered to do so by the master. The essential signal processing is located in the master, while the slaves for instance prepare the signals, output by sensors and supplied to the slaves, for data transmission to the master and optionally carry the signals output by the master for actuating final control elements. These provisions contribute to keeping the expense for circuitry in the slaves as low as possible, to enable inexpensive manufacture. The known device is contemplated in the context of a multiplexing system that is disposed in a motor vehicle. By way of example, the slaves are actuators for devices relating to passenger comfort, control units and other electrical motor vehicle components that are controlled from a central point by at least one master. The various slaves are embodied differently, so that they can meet the signal detection and signal output functions assigned to them.
The object of the invention is to provide a device for exchanging data that can be made economically.
The above objects generally are achieved according to the present invention by a device or arrangement for exchanging data between a main station (master) and a plurality of secondary stations (slave), which each have access via respective interfaces to at least one common data line, wherein: the master contains an identifier memory for receiving identifiers of the slaves; the slaves are all substantially identical and each contains one identifier memory in which an individual identifier, which is unique to the associated slave and which is to be stored in the identifier memory of the master, is stored; and the slaves each include one program memory for holding applications-specific programs intended for the respective slave.
The device of the invention for exchanging data has the advantage that all the secondary stations, hereinafter called slaves, are embodied identically, at least in a basic configuration. The various slaves differ only in an individual, one-time identifier, which is stored in the slave in the form of a sequential serial number, for instance during manufacture. The functions to be performed by the slaves are not assigned to the slaves until after the device is put into operation. The function of the slaves is defined by programs, which are stored in a memory for applications specific programs that is located in the slave. The main station, hereinafter called the master, contains an identifier memory for holding the identifiers stored in memory in the slaves, to enable identifying the slaves.
A preferred application of the device of the invention is disclosed in the context of a multiplexing system disposed for instance in a motor vehicle. One substantial advantage is the economical embodiment of the device of the invention, because a greater number of identical slaves can be manufactured. A further advantage arises in stocking of spare parts, which in the simplest case means uniformly embodied masters and the identical slaves.
Advantageous further features and embodiments of the device of the invention will become apparent from dependent device claims.
An especially advantageous provision is to equip the master with a memory for holding the applications-specific programs to be stored in the slaves. If a replacement of a slave should become necessary in the course of a repair, access to the applications-specific program contained in the master can be gained at any time, and it can be loaded in the new slave.
It is especially advantageous for each of the individual slaves to be assigned applications interfaces whose function is defined in accordance with the applications-specific programs to be stored in the applicable slave. With this provision, it is possible to adapt the number of both inputs and outputs to given requirements.
An advantageous embodiment provides that the identifier, stored in invariable form in the various slaves and contained for instance in a random access memory, is a sequential serial number assigned in production. This provision assures that if replacement of a slave should become necessary in a repair, the slaves will always have different identifiers.
An advantageous further feature provides that the master includes an interface that makes it possible for the applications-specific programs to be stored in the various slaves to be loaded from an external computer via the master into the slaves and into the memory that is possibly present in the master. With this interface it is possible in particular to transmit the identifiers of the various slaves to the master.
The interface, by way of example, is a diagnostic interface in accordance with DIN/ISO 9141. Embodying the interface as a standardized diagnostic interface enables self-diagnosis in the known device. The memory required for the diagnostic data need be present only in the master. The diagnostic data ascertained in the various slaves are transmitted to the master via the common data line, and in the master are either stored directly in the diagnosis memory or first are further processed in the context of diagnostic programs. The entire system of master and slaves thus contains only a single diagnostic interface.
The processes of the invention each enable advantageous operation of the device of the invention.
In a first process of the invention, it is provided that the identifiers of the slaves are imparted to the master via the diagnostic interface disposed in the master. This provision thus directly makes the identification process itself possible. The external computer also furnishes the applications-specific programs intended for the slaves.
In another process it is provided that the master procures the identifiers stored in the various slaves on its own, by readout of the identifiers stored in the slaves. The requisite for this process is that the slaves upon installation of the device of the invention are connected to the common data line in a specified order and are put into operation one after the other in that order. With this process, the replacement of a defective master when the slaves are intact or the replacement of at maximum all the slaves is possible.
Another process according to the invention for operating the device is directed to repair, in which a slave is replaced. From a comparison of the identifiers stored in the master with the identifiers of the slaves present before, the new slave can be ascertained, and the old identifier in the master replaced with the new identifier of the new slave.
Further advantageous features and embodiments of both the device of the invention and the processes of the invention will become apparent from the further dependent claims and in conjunction with the ensuing description.